Railway track occupancy detectors



Oct. 10, 1961 c. E. STAPLES 3,004,149

RAILWAY TRACK OCCUPANCY DETECTORS Filed Oct. 28, 1959 Light Source 6 D:p Zzgbi Beam 1 E Li lnf Responsive Device I? 4 P02 TH E I; i 5 i I H i44=- ""la,i I L -.l i

i I i 1 iv F 1) To [12d icaion or Conral Apparazzs INVENTOR.

Crawfordlfdizyks BY H15 ATTORNEY tion of Pennsylvania Filed Oct. 28,1959, Ser. No. 849,226 6 Claims. (Cl. 246-29) My invention relates to arailway track occupancy detector, and particularly to a track occupancydetector arrangement for a track section of sufficiently short lengththat it can at times be spanned by the inside pairs of wheels and axlesof the trucks of the railway car, having the greatest distance betweensaid pairs of wheels, to travel said track section.

In many railway installations such as interlockings, classificationyards, etc., it is often expedient or necessary to provide shortdetector track sections for detecting the presence of engines or railwaycars in the tracks included in the interlocking or yard. Where any suchtrack section is of such extremely short length that it can be spannedby the inside pairs of wheels and axles of the trucks of a railway carto traverse the section, it is necessary to supplement the usualdetector track circuit, provided for the section, with an additionaloccupancy detection arrangement to insure that detection of the presenceof such a car is not lost when the section is spanned by the wheels andaxles of the car. One such arran ement is shown and described in theapplication for Letters Patent of the United States of William A.Robison, Jr., Serial No. 806,120, filed April 13, 1959, for RailwaySwitch Locking Apparatus, which application is assigned to the assigneeof the present application. The apparatus of that application employs acoded light beam and a light responsive device to supplement the usualdetector track circuit in the detection of the presence of a railway carin a short track section. The coding of the light beam and the use of adecoding transformer insures that the light responsive device is intact,that is, that a short circuit, operating to retain the relay responsiveto the light beam energized when the beam is.

interrupted by a railway car, does not exist in the light responsivedevice.

It is, accordingly, one object of my present invention to provide anarrangement employing a light beam and a light responsive device tosupplement the usual detector track circuit and providing equivalentcertainty that the light responsive device is intact, but without thenecessity of coding the light beam and employing a decoding transformer,thereby providing a more economical arrangement due to the eliminationof a code generator or code transmitter, and the decoding transformer.

It is a second object of my invention to provide an arrangement of thetype described in which the light beam is normally off, therebyproviding additional economy in the conservation of the power forilluminating the light source.

Other objects and characteristic features of my invention will becomeapparent as the description proceeds.

I accomplish the foregoing objects of my invention by employing anormally deenergized light source which is energized only when it isnecessary to transmit a light beam for detection of the presence of arailway car, and an energy storing or capacitor-resistor unit to cyclecheck the closing of a front and back contact of a relay controlled by adevice responsive to the receipt of the light beam, thereby insuringthat the light responsive device is not short circuited and the relaythus continuously in a picked-up position.

Other objects and characteristic features of my invention will becomeapparent as the description proceeds.

I shall first describe one embodiment of my invention 3,064,149 PatentedOct. 16, 1961 and shall then point out the novel features thereof inclaims.

The accompanying drawing is a diagrammatic view showing one form ofapparatus embodying my invention.

Referring to the drawing, the reference character A designates a stretchof railway track including rails 1 and la divided at points D and E byinsulated joints 2 to form a track section DE which is sufficientlyshort to be spanned by the wheels and axles of a car, as previously setforth. This track section is provided with a track circuit comprising abattery 4 and a track relay TR arranged in a manner well known in theart, such that the contacts of track relay TR are in a normallypicked-up position.

In the particular embodiment of my invention shown, intrusion detectionapparatus is shown including a source of light 6 located on one side oftrack A and a cooperat ing light responsive device 8 located on theopposite side of the track, the device 8 so positioned relative to lightsource 6 as to be responsive to a light beam from said source projectedacross the track. The light source 6 and light responsive device 8 arethus arranged that light from the source will strike the device when thelight source is energized but will be interrupted by a car traversingtrack section DE.

A relay PCR of the neutral type is provided with a control circuit,including a battery 12, controlled by device 8. Contact a of relay PCRis operated to its pickedup or released positions according as device 8does or does not receive light from the source 6. Such light responsivearrangements are well known.

It should be pointed out at this time that a suitable source of directcurrent is provided for operation of apparatus other than the trackcircuit apparatus and the relay operated by the light responsive device8, this source being preferably a battery of proper voltage and capacitywhich, for the sake of simplicity, is not shown in the drawings, but itspositive and negative terminals are identified by the conventionalreference characters B and N respectively.

An additional relay designated HR is provided which is controlled by thetrack relay TR and the light beam responsive relay PCR. This relay is astick relay which is normally maintained energized by a stick circuitextending from terminal B of the battery over front contact b of relayTR, the front point of its own contact a, and through the winding of therelay to terminal N of the battery.

Relay HR is provided with a pickup circuit which is energized by acharge of current from the aforementioned energy storing orcapacitor-resistor unit 14 to be described. This pickup circuit extendsfrom the righthand side of unit 14 over the front point of contact a ofrelay TR in its picked-up position, the front point of contact a ofrelay PCR in its picked-up position and through the winding of relay HRto the left-hand side of unit 14.

Capacitor-resistor unit 14 has a charging circuit extending from batteryterminal B over the back point ofv contact a of relay PCR, the frontpoint of contact a of relay TR, and through the unit to terminal N ofthe battery. It is thus apparent that a charge of current is supplied tounit 14 to be stored when relay PCR is released and track relay TR ispicked up. The utility of such arrangement will become more apparentlater in this description.

As previously set forth the light source 6 is normally deenergized and,therefore, the light beam is extin guished. The circuit for energizingthe light source extends from terminal B of the battery over frontcontact [2 of relay TR, the back point of contact a of relay HR andthrough the filament of the light source, such filament for purpose ofsimplicity not being shown in the drawing, to terminal N of the battery.The light source is, there fore, energized when relay TR is in itspicked-up position and relay HR is in its released position as will bedescribed hereinafter. Contact I) of relay HR may be employed to controlany desired apparatus such as a track occupancy indicator, a signal, aswitch etc., but is shown in the drawing as controlling a circuit forsupplying current to indication or control apparatus. However, it is tobe'understood that a contact or contacts of relay HR can be employed tocontrol any of the apparatus well known in the art which is normallycontrolled by a contact or contacts of the track relay of a normallyenergized conventional type track circuit.

I will now describe the operation of the apparatus of my invention whena railway car capable of spanning the track section, as previously setforth, enters and proceeds through the track section DE. I will assumefor purposes of this description that the apparatus is in its normalcondition as shown in the drawing, that is, relays TR and HR are intheir picked-up positions, the light source 6 is deenergized, and relayPCR is released.

When the car enters track section D-E from either direction, the trackcircuit is shunted and track relay TR releases. The release of trackrelay TR opens the stick circuit for relay HR which also releases. Therelease of track relay TR also closes at the back point of its contact aa discharge circuit for unit 14. This circuit assures at this time thatany energy stored in unit 14 is discharged, and extends from theright-hand side of unit 14 over the back point of contact a of relay TRto the left-hand side of the unit. This is the only operation of thedetector apparatus that takes place at this time.

When the front truck of the car has proceeded completely through sectionDE and has vacated the section, and the rear truck has not yet enteredthe section, that is the wheels and axles of the car are spanning thesection, track relay TR again picks up. The picking up of track relay TRcloses over its front contact b and the back point of contact a of relayHR the energizing circuit for the light source 6. However, the lightbeam projected by the light source is interrupted by the sides of thecar so the light responsive device 8 is not actuated and relay PCRremains in its original position. A charge of energy is supplied to unit14 at this time over the back point of contact a of relay PCR and thefront point of contact a of relay TR, but no further action takes placeat this time.

When the rear truck of the car enters track section DE, track relay TRis again released, unit 14 is again discharged, and the light source 6is again deenergized. The apparatus, therefore, is temporarily in thesame condition as when the front truck of the car occupied the tracksection. When the rear truck of the car vacates the track section, relayTR again picks up, and since the energizing circuit for the light source6 is now closed and the sides of the car no longer interrupt the lightbeam, the light responsive device 8 will be actuated to cause relay PCRto be picked up by the energy supplied from battery 12. However,previous to relay PCR picking up, unit 14 will be charged over thecircuit including the back point of contact a of relay PCR and the frontpoint of contact a of relay TR. Therefore, when relay PCR picks up, thedischarge circuit for unit 14 through the winding of relay HR iscompleted and relay HR is operated to its picked-up position by theenergy stored in capacitor-resistor unit 1 The picking up of relay HRopens the energizing circuit for light source 8, the light beam isextinguished, relay PCR is subsequently released, and the apparatus isrestored to its normal condition.

It will be noted that should a short circuit occur in the lightresponsive device 8 which would cause relay PCR to be continuouslypicked up, the charging circuit for unit 14 is never completed, and,therefore, relay HR when released cannot again be picked up until theshort circuit is removed. In other words, by the arrangement of myinvention I have provided a means whereby relay PCR must close both itsback and front contact points in that order, in order that relay HR canbe picked up following a period of release of relay HR. This operationcycle checks the operation of relay PCR, and is considered equivalent tothe operation of a code following relay by a coded light beam.

While I have shown and described only one form of apparatus embodying myinvention, it should be understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a track occupancy detection arrangement for a section of railwaytrack capable of being spanned by the Wheels and axles of a railway car,the combination comprising, a track circuit for said track sectionincluding a source of current and a track relay actuated from a firstposition to a second position when the track section is occupied, alight responsive device, a normally deenergized light source so disposedin relation to said light responsive device and said track section thata beam of light projected from the source to the device is interruptedwhen a portion of the track section is occupied, a second relay, a stickcircuit for said second relay including one of its own front contactsand a first contact of said track relay closed in the first position ofthe track relay, an energizing circuit for said light source includingsaid first contact of said track relay and a back contact of said secondrelay, a third relay, means controlled by said light responsive devicefor picking up said third relay when said device is receiving light fromsaid source, an energy storing device, a circuit for storing a charge ofenergy in said energy storing device, said circuit including a backcontact of said third relay and a second contact of said track relayclosed in the first position of the track relay; and a pickup circuitfor said second relay including said energy storing device, said secondcontact of said track relay, and a front contact of said third relay.

2. In a track occupancy detector arrangement for a section of railwaytrack capable of being spanned by the wheels and axles of a railway carand including a track circuit for said section including a normallypicked-up track relay, the combination comprising, a normallydeenergized light source capable when energized of projecting a lightbeam across said section of track, a light responsive device on theopposite side of said section of track from said light source andresponsive to said light beam, a normally released second relay, anormally picked-up third relay, means controlled by said track relay forreleasing said third relay when the track relay is released, meanscontrolled by said track relay and said third relay for energizing saidlight source when the track relay and the third relay are picked-up andreleased respectively, means controlled by said light responsive devicefor picking up said second relay when the device responds to said lightbeam, an energy storing device, means controlled by said track relay andsaid second relay for storing a charge of energy in said energy storingdevice when said track relay is picked up and said second relay isreleased; and means controlled by said energy storing device, said trackrelay, and said second relay for picking up said third relay only when acharge of energy is stored in the energy storing device, and the trackrelay and the second relay are both picked up.

3. In a track occupancy detector arrangement for a section of railwaytrack capable of being spanned by the wheels and axles of a railway carand including a track circuit for said section including a source ofcurrent and a normally energized track relay, the combinationcomprising, a normally deenergized light source on one side of saidtrack section and capable when energized of projecting a light beamacross the section, a light responsive device on the opposite side ofsaid track section and so arranged as to receive said light beam whenprojected, a normally deenergized second relay, means controlled by saiddevice for energizing said second relay when said light beam is receivedby the device, a third relay, a stick circuit for said third relayincluding a first front contact of said track relay, an energizingcircuit for said light source including said first front contact of saidtrack relay and a back contact of said third relay, a capacitor, anenergizing circuit for said capacitor including a back contact of saidsecond relay and a second front contact of said track relay, and anenergizing circuit for said third relay including said second frontcontact of the track relay and a front contact of said second relay.

4. In a track occupancy detector arrangement for a section of railwaytrack capable of being spanned by the wheels and axles of a railway carand including a track circuit for said section including a source ofcurrent and a normally energized track relay, the combinationcomprising, a normally energized second relay, means controlled by saidtrack relay for maintaining said second relay energized when it is onceenergized and so long as said track relay is energized, a light sourcearranged when energized to project a light beam across the rails of saidtrack section, a light responsive device on the opposite Side of saidtrack section and arranged to receive said light beam when projected, anormally deenergized third relay, means controlled by said track relayand said second relay for energ zing said light source when said trackrelay is energized and said second relay is deenergized, meanscontrolled by said light responsive device for energizing said thirdrelay when the device receives said light beam, an energy storingdevice, means controlled by said track relay and said third relay forstoring energy in said storing device when said track relay is energizedand said third relay is deenergized; and means controlled by said energystoring device, said track relay, and said third relay for energizingsaid second relay When energy is stored in the energy storing device,and the track relay and the third relay are both energized.

5. In a track occupancy detector arrangement for a section of railwaytrack capable of being spanned by the wheels and axles of a railway carand including a track circuit for said section including a source ofcurrent and a track relay energized when the track section isunoccupied,

the combination comprising, a light source arranged when energized toproject a light beam across the rails of said track section, a lightresponsive device on the opposite side of said track section andarranged to receive said light beam when projected, a normallydeenergized second relay, means controlled by said light responsivedevice for energizing said second relay when the device receives saidlight beam, a normally energized stick relay, means controlled by saidtrack relay for deenergizing said stick relay when the track relay isdeenergized, means controlled by said track relay when energizedfollowing a period of deenergization for energizing said light source,and means controlled by said track relay and said second relay forreenergizing said stick relay only when the track relay is energized andthe second relay is thereafter energized.

6. A track occupancy detection arrangement for a sec-- tion of railwaytrack capable of being spanned by the wheels of a railway car,comprising, in combination, a track occupancy detection device fordetecting the presence in said track section of the wheels of a railwaycar and actuated from a first position to a second position by theoccupancy of any part of said track section by the wheels of a railwaycar, a first relay, means controlled by said detection device formaintaining said first relay energized when once energized and only solong as the device occupies its first position, a second relay, meanscontrolled by said detection device and said first relay for energizingsaid second relay only when the first relay is deenergized and thedetection device again occupies its first position following the passageof said railway car through said track section, a capacitor, meanscontrolled by said detection device and said second relay for chargingsaid capacitor when the detection device occupies its first positionfollowing the passage of said railway car through said track section andprevious to the energization of the second relay, and means controlledby said second relay and said capacitor for reenergizing said firstrelay when the second relay is energized following said passage of therailway car.

References Cited in the file of this patent UNITED STATES PATENTS1,839,784 Livingston Jan. 5, 1932 2,465,794 Fereday Mar. 29, 19492,549,146 Van Horn n Apr. 17, 1951 2,607,001 Jerome Aug. 12, 19522,654,081 Staples Sept. 29, 1953

